Formation Sampling Methods and Systems

ABSTRACT

The present disclosure relates to a formation sampling method that includes disposing a downhole tool comprising a packer and an expandable probe within a wellbore. The method also includes performing pressure transient testing by setting the expandable packer and the probe to engage a wall of the wellbore and measuring a pressure response at the expandable packer and the probe while withdrawing formation fluid into the downhole tool through the expandable packer. The method further includes monitoring a contamination level of the formation fluid during the pressure transient testing, and performing formation sampling with the probe in response to determining that the monitored contamination level meets a predetermined threshold.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of, and priority to, U.S. patentApplication Ser. No. 62/175,987, filed Jun. 15, 2015, which applicationis expressly incorporated herein by this reference in its entirety.

BACKGROUND OF THE DISCLOSURE

Wellbores (also known as boreholes) are drilled to penetratesubterranean formations for hydrocarbon prospecting and production.During drilling operations, evaluations may be performed of thesubterranean formation for various purposes, such as to locatehydrocarbon-producing formations and manage the production ofhydrocarbons from these formations. To conduct formation evaluations,the drill string may include one or more drilling tools that test and/orsample the surrounding formation, or the drill string may be removedfrom the wellbore, and a wireline tool may be deployed into the wellboreto test and/or sample the formation. These drilling tools and wirelinetools, as well as other wellbore tools conveyed on coiled tubing, drillpipe, casing or other conveyers, are also referred to herein as“downhole tools.”

Formation evaluation may involve drawing fluid from the formation into adownhole tool for testing and/or sampling. Various devices, such asprobes and/or packers, may be extended from the downhole tool to isolatea region of the wellbore wall, and thereby establish fluid communicationwith the subterranean formation surrounding the wellbore. Fluid may thenbe drawn into the downhole tool using the probe and/or packer. Withinthe downhole tool, the fluid may be directed to one or more fluidanalyzers and sensors that may be employed to detect properties of thefluid.

SUMMARY

The present disclosure relates to a formation sampling method thatincludes disposing a downhole tool that has an expandable packer and anextendable probe within a wellbore, performing pressure transienttesting by setting the expandable packer and the probe to engage a wallof the wellbore and measuring a pressure response at the expandablepacker and the probe while withdrawing formation fluid into the downholetool through the expandable packer, monitoring a contamination level ofthe formation fluid during the pressure transient testing, andperforming formation sampling with the probe in response to determiningthat the monitored contamination level meets a predetermined threshold.

The present disclosure also relates to a downhole tool that includes anexpandable packer and an extendable probe. The expandable packerincludes a drain for withdrawing a first portion of formation fluid intothe downhole tool, and the extendable probe includes a sample inlet anda guard inlet for withdrawing a second portion of formation fluid intothe downhole tool. The downhole tool also includes a fluid analyzer tomonitor a contamination level of the first portion of the formationfluid and a controller. The controller is designed to executeinstructions stored within the downhole tool to: perform pressuretransient testing by setting the expandable packer and the probe toengage a wall of the wellbore and measuring a pressure response at theexpandable packer and the probe while withdrawing the first portion ofthe formation fluid into the downhole tool through the expandablepacker; and perform formation sampling with the extendable probe inresponse to determining that the monitored contamination level meets apredetermined threshold.

BRIEF DESCRIPTION OF THE DRAWINGS

The present disclosure is understood from the following detaileddescription when read with the accompanying figures. It is emphasizedthat, in accordance with the standard practice in the industry, variousfeatures are not drawn to scale. In fact, the dimensions of the variousfeatures may be arbitrarily increased or reduced for clarity ofdiscussion.

FIG. 1 is a schematic view of an embodiment of a wellsite system thatmay employ formation sampling systems and methods, according to aspectsof the present disclosure;

FIG. 2 is a schematic representation of an embodiment of a downhole toolfor performing formation sampling, according to aspects of the presentdisclosure;

FIG. 3 is a schematic representation of an embodiment of the expandablepacker shown in FIG. 2, according to aspects of the present disclosure;

FIG. 4 is a schematic representation of an embodiment of the extendableprobe shown in FIG. 2, according to aspects of the present disclosure;

FIG. 5 is a flowchart depicting a formation sampling method, accordingto aspects of the present disclosure; and

FIG. 6 is flowchart depicting another formation sampling method,according to aspects of the present disclosure.

DETAILED DESCRIPTION

It is to be understood that the present disclosure provides manydifferent embodiments, or examples, for implementing different featuresof various embodiments. Specific examples of components and arrangementsare described below to simplify the present disclosure. These are, ofcourse, merely examples and are not intended to be limiting.

The present disclosure relates to methods and systems for formationsampling where the cleanup phase is accelerated by using an expandablepacker for at least a portion of the cleanup phase. During formationtesting and sampling, the fluid initially withdrawn into the downholetool may be contaminated with drilling fluid, mud cake and othercomponents. However, as formation testing and sampling continues, thelevels of contaminants are reduced as fluid is drawn into the tool fromdeeper within the formation such that virgin formation fluid primarilyenters the downhole tool. According to certain embodiments, fluid may beconsidered to be representative of virgin formation fluid whencontamination levels are at or below a predetermined level, such as 5%,4%, or 3%. At these levels, the properties of the fluid may closelycorrelate to properties of the virgin formation fluid, and therefore thesample may be representative of the virgin formation fluid. The “cleanupphase” is the period during which fluid is withdrawn into the downholetool to reduce the contamination level to the predetermined level.According to certain embodiments, a downhole tool may include both anexpandable packer and an extendable probe for withdrawing fluid into theformation. The expandable packer may be employed to withdraw relativelylarge amounts of fluid into the downhole tool, as compared withextendable probes, to accelerate the cleanup phase. Once an acceptablecontamination level is detected, the extendable probe may be employed towithdraw substantially virgin formation fluid into the tool for testingand/or sampling.

FIG. 1 depicts an example of a wellsite system 100 that may employ theformation testing and sampling systems and techniques described herein.A downhole tool 200 is suspended in a wellbore 202 from the lower end ofa multi-conductor cable 204 that is spooled on a winch at the surface.The cable 204 is communicatively coupled to an electronics andprocessing system 206. The electronics and processing systems 206 mayone or more processors, volatile memory (e.g., random-access memory)and/or non-volatile memory (e.g., flash memory and a read-only memory(ROM)). Coded application instructions (e.g., software that may beexecuted by the processor to enable the control and analysisfunctionality described herein) and data may be stored in the memory. Asshown in FIG. 1, the downhole 200 is conveyed on a wireline; however, inother embodiments, the downhole tool may be conveyed on a drill string,a wired drill pipe, a combination of wired drill pipe and wireline, orother suitable types of conveyance.

The downhole tool 200 includes an elongated body 208 that houses modules209, 210, 211, 212, 213, 214, 222, and 224 that provide variousfunctionalities including fluid sampling, fluid testing, operationalcontrol, and communication, among others. For example, the module 211may be a power and electronics module that provides electrical power forthe downhole tool 200. The modules 209 and 210 may be pump modules thatdirect formation fluid through the downhole tool. Further, the modules212 and 213 may be fluid analysis modules that include opticalspectrometers and other sensors that can be employed to determineproperties of the formation fluid. In other embodiments additionalmodules may be included in the downhole tool 200 to provide furtherfunctionality such as resistivity measurements, operational control,communications, coring, and/or imaging, among others. Moreover, incertain embodiments, the relative positions and arrangement of themodules within the downhole tool 200 may vary.

As shown in FIG. 1, the module 214 is a sampling probe module 214 thathas a selectively extendable probe 216 and backup pistons 218 that arearranged on opposite sides of the elongated body 208. The extendableprobe 216 is configured to selectively seal off or isolate selectedportions of the wall 203 of the wellbore 202 to fluidly couple to theadjacent formation 220 and to withdraw fluid samples from the formation220. The probe 216 may include a single inlet or multiple inletsdesigned for guarded or focused sampling.

The downhole tool 200 also includes an expandable packer module 224 thathas an expandable packer 226 that can be expanded radially outward fromthe downhole tool 200 to engage the wall 203 of the wellbore 202. In theexpanded position, as shown in FIG. 1, the packer 226 circumferentiallyengages the wall 203 of the wellbore to fluidly couple to the adjacentformation 220 and to withdraw fluid samples from the formation 220.According to certain embodiments, the packer 226 extends around theentire circumference of the wellbore to seal a cross-section of thewellbore 202.

The formation fluid may be withdrawn into the tool 200 through theextendable probe 216 and/or through the expandable packer 226. Withinthe tool, the formation fluid may be analyzed to determine fluidproperties, such as contamination levels, viscosity, fluid density,optical density, and compressibility, among others. The formation fluidmay then be expelled to the wellbore through a port in the body 208 orthe formation fluid may be sent to a fluid sampling module 222. Thefluid sampling module may include sample chambers that store theformation fluid. In the illustrated example, the electronics andprocessing system 206 and/or a downhole control system are configured tocontrol the extendable probe assembly 216 and the expandable packer 226and may also control the formation testing and sampling methodsdescribed herein.

FIG. 2 is a schematic diagram of a portion of the downhole tool 200. Thedownhole tool 200 includes the probe module 214, which includes theextendable probe 216 for directing formation fluid into the downholetool 200. The probe module 214 includes a sample flowline 230 thatdirects the formation fluid from a sample inlet 231 to a main flowline232 that extends through the downhole tool 200. The probe module 214also includes a pretest pump 234 and pressure gauges 236 and 238 thatmay be employed to conduct formation pressure tests. An equalizationvalve 240 may be opened to expose the flowline 230 to the pressure inthe wellbore, which in turn may equalize the pressure within thedownhole tool 200. Further, an isolation valve 242 may be closed toisolate the formation fluid within the sample flowline 230 and/or toisolate the sample flowline 230 from the main flowline 232. Theisolation valve 242 may be opened to direct the formation fluid from thesample flowline 230 to the main flowline 232.

The probe module 214 also includes a guard flowline 244 that directs theformation fluid from a guard inlet 245 to the main flowline 232.According to certain embodiments, the guard inlet 245 may be disposedcircumferentially around the sample inlet 231 to provide focusedsampling. During sampling, the more contaminated formation fluid mayflow through the guard inlet 245 and the less contaminated formationfluid may flow through the sample inlet 231. An isolation valve 246 maybe closed to isolate the formation fluid within the guard flowline 244and/or to isolate the guard flowline 244 from the main flowline 232. Theisolation valve 246 may be opened to direct the formation fluid from theguard flowline 244 to the main flowline 232. A valve 249 may be disposedbetween the sample flowline 230 and the guard flowline 244. The valve249 may be opened to allow the fluid from the flowlines 230 and 244 tomix, for example, during an initial cleanup phase where formation fluidentering the downhole tool 200 is directed through the tool and returnedto the wellbore. Once an acceptable contamination level is reached, thevalve 249 may be closed to isolate the fluid within the sample flowline230 from the fluid within the guard flowline 244.

A valve 248 also may be disposed in the main flowline 232 to isolate afirst portion 250 of the main flowline 232 (e.g., above the valve 248)from a second portion 252 of the main flowline (e.g., below the valve248). During sampling, the valve 248 may be closed and formation fluidfrom the sample flowline 230 may be directed through the first portion250 of the main flowline 232 to the fluid analysis module 212 and thesample module 222, while formation fluid from the guard flowline 244 isdirected through the second portion 252 of the main flowline 232 to thefluid analysis module 254 and the pump module 209.

The first portion 250 of the main flowline 232 directs the formationfluid through the downhole tool 200 to the fluid analysis module 212 andthe second portion 252 directs the formation fluid through the downholetool 200 to the fluid analysis module 213. Each fluid analysis module212 and 213 includes a fluid analyzer 254 a or 254 b that can beemployed to provide downhole fluid measurements. For example, the fluidanalyzers 254 a and 254 b may include an optical spectrometer and/or agas analyzer designed to measure properties such as, optical density,fluid fluorescence, fluid composition, and the fluid gas oil ratio(GOR), among others. One or more additional measurement devices, such astemperature sensors, pressure sensors, viscosity sensors, resistivitysensors, chemical sensors (e.g., for measuring pH or H₂S levels), andgas chromatographs, also may be included within the fluid analyzers 254a and 254 b.

In certain embodiments, the fluid analysis modules 212 and 213 mayinclude a controller 256 a or 256 b such as a microprocessor or controlcircuitry, designed to calculate certain fluid properties based on thesensor measurements. The controllers 256 a and 256 b may include memorythat stores coded application instructions (e.g., software that may beexecuted by the controller to enable the control and analysisfunctionality described herein) and data 130 (e.g., acquiredmeasurements and/or the results of processing). For example, thecontrollers 256 a and 256 b may calculate contamination levels of theformation fluid withdrawn into the tool through the sample flowline 230and the guard flowline 244. Further, in certain embodiments, thecontrollers 256 a and 256 b may govern sampling operations based on thefluid measurements or properties. Moreover, in other embodiments, thecontrollers 256 a and 256b may be disposed within another module of thedownhole tool 200, or may be combined into a single downhole controller.

The downhole tool 200 also includes the pump modules 209 and 210. Eachpump module 209 and 210 includes a pump 258 a or 258 b designed toprovide motive force to direct the fluid through the downhole tool 200.According to certain embodiments, the pumps 258 a and 258 b may behydraulic displacement units that receive fluid into alternating pumpchambers. A valve block 260 a or 260 b may direct the fluid into and outof the alternating pump chambers. The valve blocks 260 a and 260 b alsomay direct the fluid exiting the pump 258 a and 258 b through the mainflowline 232 or may divert the fluid to the wellbore through flowlines262 a and 262 b connected to ports 264 a and 264 b in the body 208 ofthe downhole tool 200. Further, in certain embodiments, the valve blocks260 a and 260 b may direct fluid from the wellbore into the downholetool 200 through the ports 264 a and 264 b.

The downhole tool 200 also includes one or more sample modules 222designed to store samples of the formation fluid within a sample chamber266. As shown in FIG. 2, a single sample chamber 266 is included withinthe sample module 222. However, in other embodiments, multiple samplechambers may be included within the sample module 222 to provide forstorage of multiple formation fluid samples. Further, in otherembodiments, multiple sample modules 222 may be included within thedownhole tool 200. Moreover, other types of sample chambers, such assingle phase sample bottles, among others, may be employed in the samplemodule 222.

The sample module 222 includes a valve 268 that may be actuated todivert the formation fluid into the sample chamber 266. The samplechamber 266 includes a floating piston 270 that divides the samplechamber into two volumes 272 and 274. As the formation fluid flowsthrough the main flowline 232, the valve 268 may be actuated to divertthe formation fluid into the volume 272. In certain embodiments, thepump 258 a or 258 b may provide the motive force to direct the fluidthrough the main flowline 232 and into the sample chamber 266. Theformation fluid may be stored within the volume 272 and, in certainembodiments, may be brought to the surface for further analysis. Thesample module 222 also may include a valve 276 that can be opened toexpose the volume 274 of the sample chamber 266 to the annular pressurethrough a port 278 in the body 208 of the downhole tool 200. In certainembodiments, the valve 276 may be opened to allow buffer fluid to exitthe volume 274 to the wellbore, which may provide backpressure duringfilling of the volume 272 that receives formation fluid. In otherembodiments, the volume 274 may be filled with a low pressure gas thatprovides backpressure during filling of the volume 272.

The downhole tool 200 also includes the packer module 224. According tocertain embodiments, the packer module 224 may be disposed directlyadjacent to the probe module 214. The adjacent and close spacing betweenthe packer module 224 and the probe module 214 may enable both thepacker 226 and the probe 216 to be employed to sample from a similarpart of the formation 220. For example, as shown in FIG. 1, the packer228 may engage the wellbore wall 203 at a first location 228 within thewellbore, and the probe 216 may engage the wellbore wall 203 at a secondlocation 229 within the wellbore. The locations 228 and 229 may berelatively close to one another, for example, within approximately 10 orfewer feet of one another, or more specifically, within approximately 4feet of one another.

The packer module includes the packer 226 that may be expanded tocontact the wellbore wall. The packer 226 includes drains 280 that maybe disposed against the wellbore wall when the packer 226 is in theexpanded position. According to certain embodiments, the drains 280 maybe spaced circumferentially around the packer 226. Formation fluid maybe withdrawn into the downhole tool 200 through the drains 280 anddirected through a sample flowline 282 to the main flowline 232. Thepump 260 a or 260 b may provide the motive force for withdrawingformation fluid into the downhole tool through the drains 280. Theformation fluid may then be directed through the second portion 252 ofthe main flowline and the first portion 250 of the main flowline 232 tothe sample chamber 266. Further, in certain embodiments, the formationfluid may be directed through the main flowline 232 to one or both ports264 a and 264 b to be returned to the wellbore. A valve 284 may bedisposed in the sample flowline 282 and may be closed to isolate thesample flowline 282 from the main flowline 232. The valve 284 may beopened to direct formation fluid from the drains 280 through the sampleflowline 282 to the main flowline 232.

The packer module 224 also includes an inflation flowline 286 that maybe employed to inflate the packer 226. A valve 288 may be disposed inthe inflation flowline 286 and may be opened to enable fluid to flowthrough the inflation flowline 286 to inflate the packer 226. Accordingto certain embodiments, fluid from the wellbore may be pumped into thedownhole tool 200 through a port 264 a or 264 b by pump 258 a or 258 b.The fluid may be directed through the main flowline 272 and into theinflation flowline 286 to inflate the packer 226. The valve 288 may thenbe closed to maintain the packer 226 in the inflated position, forexample during formation testing sampling. In certain embodiments, theinflation flowline 286 also may be employed to deflate the packer 226.For example, the valve 288 may be opened and pump 258 a or 258 b may beemployed to direct fluid from the packer 226, through the flowline 286and main flowline 272 to exit the downhole tool 200 through the port 264a or 260 b.

FIG. 3 depicts an embodiment of the packer module 224. The packer 226includes an outer structural layer 300 that is expandable in a wellboreto form a seal with the surrounding wellbore wall or casing. Disposedwithin an interior of the outer structural layer 300 is an inner,inflatable bladder 302 disposed within an interior of the outerstructural layer 300. For ease of illustration, FIG. 3 depicts thepacker 226 with a portion of the outer structural layer 300 cut away toshow the internal components of the outer structural layer 300 and theinflatable bladder 302. The inflatable bladder 302 can be formed inseveral configurations and with a variety of materials, such as a rubberlayer having internal cables. In one example, the inflatable bladder 302is selectively expanded by fluid delivered via an inner mandrel 304.According to certain embodiments, fluid may be delivered within theinner mandrel 304 via the inflation flowline 286, as described abovewith respect to FIG. 2. The packer 226 also includes a pair ofmechanical fittings 306 that are mounted around the inner mandrel 304and engaged with axial ends 308 of the outer structural layer 300.

The outer structural layer 300 includes the drains 280 through whichfluid may be drawn into the packer 226 from the subterranean formation.Further, in certain embodiments, fluid also may be directed out of thepacker 226 through the drains 280. The drains 280 may be embeddedradially into a sealing element or seal layer 310 of the outerstructural layer 300. By way of example, the seal layer 310 may becylindrical and formed of an elastomeric material selected forhydrocarbon based applications, such as a rubber material. As shown inFIG. 3, tubes 312 may be operatively coupled to the drains 280 fordirecting the fluid in an axial direction to one or both of themechanical fittings 306. The tubes 312 may be aligned generally parallelwith a packer axis 314 that extends through the axial ends of outerstructural layer 300. The tubes 312 may be at least partially embeddedin the material of sealing element 310 and thus may move radiallyoutward and radially inward during expansion and contraction of outerlayer 300.

The tubes 312 are coupled to moveable members 316 that direct fluid fromthe tubes 312 to the interior of the mechanical fittings 18, where thefluid is directed to the main flowline 232 (FIG. 2). By way of example,each movable member 316 may be pivotably coupled to its correspondingmechanical fitting 306 for pivotable movement about an axis generallyparallel with packer axis 314. In the illustrated embodiment, multiplemovable members 316 are pivotably mounted to each mechanical fitting306. The movable members 316 are designed as flow members that allowfluid flow between the tubes 312 and an interior of the mechanicalfittings 306. In particular, certain movable members 316 are coupled tocertain tubes 312 extending to the drains 280, allowing fluid from thedrains 280 to be routed to the interior of the mechanical fittings 306,which may direct the fluid to the sample flowline 282 (FIG. 2). Further,in certain embodiments, the movable members 316 also may direct fluidfrom the interior of the mechanical fittings 306 to the tubes 312 to beexpelled from the packer 226 through the drains 280. The movable members316 are generally S-shaped and designed for pivotable connection withboth the mechanical fitting 306 and the corresponding tubes 312. As aresult, the movable members 316 can be pivoted to allow the packer 226to expand and contract.

FIG. 4 depicts an embodiment of the probe module 214. During a samplingoperation, an intake 400 of the probe 216 may be extended intoengagement with the wellbore wall 203 (FIG. 1). According to certainembodiments, the intake 400 may be constructed of an elastomericmaterial and may be mounted on a plate 412 coupled to pistons 414. Thepistons 414 may be actuated to extend the plate 412 and intake 400 awayfrom the body 208 of the downhole tool 200 to place the intake 400 intoengagement with the wall 203 of the wellbore 202.

The intake 400 includes the sample inlet 231 and the guard inlet 245.The sample inlet 231 is disposed in a central region of the intake 400,and the guard inlet 245 is disposed in the annular region surroundingthe sample inlet 231. During operation, formation fluid 402 may be drawnfrom a sampling zone 404 (e.g., at the wall 203 of the wellbore 202)into the intake 400. The formation fluid 402 near the center of thesampling zone 404 may be drawn into the sample inlet 231, and theformation fluid 402 near the outside edge of the intake 400 and samplingzone 404 may be drawn into the guard inlet 245. In an example samplingoperation, debris of mud cake 406 on or at the wall 203 may be initiallydrawn into the intake 400. As pumping continues, the filtrate fluid 408adjacent to the wall 203 may be drawn into the intake 400. The debrisand the filtrate fluid may be drawn into the intake 400 during thecleanup phase of formation sampling. As pumping further continues, thevirgin formation fluid 410 adjacent to and behind the filtrate fluid 408may be drawn into the intake 400.

The sample inlet 231 directs formation fluid to the sample line 230, andthe guard inlet 245 directs formation fluid to the guard line 244. Asdescribed above with respect to FIG. 2, the fluid analyzers 254 a and254 b may determine properties of the formation fluid including thecontamination levels. When the contamination level falls below anacceptable level, formation fluid may be directed through the sampleflowline 230 to a sample chamber 266.

FIGS. 5 and 6 are flowcharts depicting methods 500 and 600 that may beemployed to perform formation sampling while using the packer 226 toaccelerate the cleanup phase. According to certain embodiments, themethods may be executed, in whole or in part, by the controllers 256 aand 256 b. For example, the controllers 256 a and 256 b may execute codestored within circuitry of the controllers 256 a and 256 b, or within aseparate memory or other tangible readable medium, to perform themethods 500 and 600. Further, in certain embodiments, the controllers256 a and 256 b may operate in conjunction with a surface controller,such as the electronics and processing system 206 (FIG. 1), which mayperform one or more operations of the methods 500 and 600.

Referring to FIG. 5, the method 500 may begin by performing pressuretransient testing (block 502). According to certain embodiments, thepressure testing may determine vertical and/or horizontal permeabilityand may include a vertical interference test (VIT) or an intervalpressure-transient test (IPTT), or both. The pressure testing may beginby setting (block 504) the packer 226 and the probe 216. For example,the downhole tool 200 may be conveyed to a desired location within thewellbore 202 and the probe 216 may be extended to engage the wall 203 ofthe wellbore 202. The packer 226 also may be expanded, for example, bydirecting wellbore fluid into the packer 226 though the inflationflowline 286. Pretests may also be performed at the packer 226 and theprobe 216, as described further below to verify sealing with thewellbore wall 203.

In certain embodiments, the packer 226 and the probe 216 may be setsimultaneously; however in other embodiments, the packer 226 and theprobe 216 may be set (block 504) sequentially, with either the packer226 or the probe 216 being set first. In one embodiment, the packer 226may be set first and a pretest may be performed for the packer 226 byclosing isolation valve 248, opening valve 284, and operating the pump258 b to draw formation fluid into the downhole tool 200 through thedrains 280 and sample flowline 282. The formation fluid may then beexpelled to the wellbore through the port 264 b. During the packerpretest (e.g., while pumping formation fluid through the sample flowline282), the probe 216 may be set by extending the probe 216 to thewellbore wall 203 and performing a pretest at the probe 216. Forexample, to perform the probe pretest, the valves 242 and 246 may beclosed and the pump 234 may be operated to withdraw formation fluid intothe downhole tool 200 through the inlets 245 and 231.

During the pretests, pressures may be monitored to determine when thepressures within the flowlines reaches formation pressure. For example,pressure gauges 236 and/or 238 may be employed to monitor the pressureduring the probe pretest, while a pressure gauge within the fluidanalyzer 254 b may be employed to monitor the pressure during the packerpretest. Once formation pressures are detected at both the packer 226and the probe 216, the pretests may be complete.

In response to detecting completion of the pretests, the controllers 256a, 256 b, and/or 206 may set the downhole tool 200 to begin pumping(block 506) solely through the packer 226. For example, operation of thepretest pump 234 may cease and valve 248 may be openend. Valves 242 and246 may be closed to isolate the probe 216 from the main flowline 232,while the valve 284 remains open to allow fluid to enter the downholetool 200 through the packer 226. One or both pumps 258 a and 258 b maythen be operated to withdraw fluid into the packer 226 through thedrains 280 and the sample flowline 282.

During withdrawal of fluid into the packer 226, the pressure may bemeasured (508) at the packer 226 and the probe 216. For example,pressure gauges 236 and/or 238 may be employed to measure the pressureresponse at the probe 216. Note that because valves 242 and 246 andclosed and pump 234 is not operating, no fluid is withdrawn into theprobe 216. However, the formation pressure response can be measured atthe probe 216 because the flowlines 230 and 244 are exposed to theformation. Pressures may also be measured at the packer 226, forexample, using pressure sensors within the fluid analyzers 254 a and 254b. Further, in other embodiments pressure sensors may be coupled to thedrains 280 to measure pressures detected at the individual drains 280.One or more drains 280 of the packer 226 may operate as sink port andthe probe 216 may operate as an observation port. Further, in certainembodiments, other drains 280 of the packer 226 may also function asobservation ports. The pressure measurements from the packer 226 and theprobe 216 can be employed for pressure transient analysis to determinehorizontal and/or vertical permeabilities and anisotropies.

During the pressure transient testing (block 502), the contaminationlevel of the formation fluid may also be monitored (block 509). Forexample, during withdrawal of fluid into the packer 226, properties ofthe formation fluid flowing through the downhole tool may be measured todetermine when the contamination level meets a predetermined threshold.For example, the fluid analyzers 254 a and 254 b may measure fluidproperties, such as optical densities and compositions, to determine thecontamination level. Further, in certain embodiments, other propertiessuch as viscosity, compressibility, resistivity, fluid density, amongothers may be employed to determine when an acceptable contaminationlevel is reached. A more detailed description of contaminationmonitoring can be found in commonly assigned U.S. Pat. No. 8,555,968 toZazovsky et al., which is hereby incorporated by reference herein in itsentirety for all purposes.

In response to determining that the contamination level is at or below adesired level, pumping may cease and the packer 226 and probe 216 may beretracted (block 510). For example, as shown in FIG. 2, the inflationfluid may exit the packer 226 through the flowline 286 to retract thepacker 226. In certain embodiments, mechanical springs also may beemployed to retract the packer 226. For the probe 216 as shown in FIG.3, the pistons 414 (FIG. 4) may be employed to retract the intake 400away from the wellbore wall 203 and towards the body 208 of the downholetool 200. The tool may then be moved within the wellbore 202 to set theprobe 216 at the previous location of the packer 226 (block 512). Forexample, as shown in FIG. 1, the cable 204 may be employed to convey thedownhole tool 200 further within the wellbore 202 so that the probe 216is disposed at the previous packer location 228. In other embodiments,the probe module 214 may be disposed on the downhole tool 200 below thepacker module 224, and in these embodiments, the downhole tool 200 maybe retracted within the wellbore 202 to place the probe 216 at theprevious packer location. In further embodiments, the probe 216 may beset in the vicinity (e.g., within 1 foot, 2 feet, 3 feet, or 4 feet) ofthe previous location of the packer 228. By disposing the probe 216 atthe previous packer location 228, the probe 216 takes advantage of thecleanup provided by the packer 226. However, in certain situations, theprobe 216 may be able to obtain a better seal with the mudcake in thevicinity of the previous location of the packer 228, but not at theprevious location of the packer 228 where the mudcake may have beenaffected by the packer 226. By disposing the probe 216 in the vicinityof the previous location of the packer 228, the probe 216 still 216takes advantage of the cleanup provided by the packer 226.

Once the probe 216 is disposed at the previous packer location 228 or inthe vicinity of the previous packer location 228, the probe 216 may beextended to engage the wellbore wall 203. Formation sampling may then beperformed (block 514) using the probe 216. For example, as shown in FIG.2, the probe 216 may be operated in a “split-flow” configuration wherethe sample flow line 230 is isolated from the guard flowline 244 toallow for focused sampling. In particular, valves 242 and 246 may beopened and pumps 258 a and 258 b may be operated to direct formationfluid into the downhole tool 200 through the sample inlet 231 and theguard inlet 245. The valves 248 and 249 may be closed so that theformation fluid flowing through the sample flowline 230 remains isolatedfrom the formation fluid flowing through the guard flowline 244. Asnoted above with respect to FIG. 3, the sampling flowline 230 mayeffectively capture the formation fluid 402 concentrated in the centralarea of the intake 400. The formation fluid 402 concentrated in thecentral area of the intake 400 may primarily include the virginformation fluid 410, and the formation fluid 402 concentrated around theperimeter of the intake 400 may include the mudcake 406, the filtratefluid 408, and/or the virgin formation fluid 410. Thus, the separationof the sample flowline 230 and the guard flowline 244, allows for aportion of the formation fluid that contains primarily virgin formationfluid 410 to be separated from the remaining formation fluid that may becontaminated with mudcake 406 and filtrate fluid 408.

The formation fluid flowing through the guard flowline 244 may bedirected through the second portion 252 of the main flowline 232 andthrough the fluid anlayzer 254b, while the formation fluid flowingthrough the sample flowline 230 may be directed through the firstportion 250 of the main flowline 232 and through the fluid anlayzer 254a. The contamination levels, as well as other properties, may bemeasured and monitored by the fluid analyzers 254 a and 254 b. Duringthis measurement and monitoring phase, the formation fluid may beexpelled to the wellbore through the ports 264 a and 264 b. When thefluid analyzer 254 a determines that the formation fluid flowing throughthe sample flowline 230 has a contamination level below a desired level,the formation fluid properties measured by the fluid analyzer 254 aduring this time may be representative of properties of the virginformation fluid. In certain embodiments, valve 268 may also be openedand a portion of the formation fluid may be directed into the samplechamber 266 for storage and further analysis at the surface.

The method 500 described above allows a majority of the cleanup phase tobe performed using the packer 226 while performing pressure testing(block 502). Accordingly, the pumping time for performing sampling(block 514) may be reduced because contamination levels may reach adesired level more quickly because a large portion of the contaminatedformation fluid may be removed by the packer 226 during the pressuretransient testing.

FIG. 6 depicts another method 600 for performing formation samplingwhile using the packer 226 to accelerate the cleanup phase. The methodmay begin by performing pressure testing (block 502) as described abovewith respect to FIG. 5. As described in detailed above, the pressuretesting may include setting (block 504) the packer 226 and the probe216; pumping (block 506) fluid through the packer 226; measuring (block508) pressures at the packer 226 and the probe 216; and monitoring(block 509) a contamination level of the formation fluid during thepressure testing. However, rather than retracting (block 510) the packerand the probe when the contamination level meets a predetermined level,the method 600 may continue by performing (block 602) sampling when thecontamination level meets a predetermined level.

As shown in FIG. 6, sampling may be performed (block 602) without movingthe downhole tool 200 to another location and without retracting thepacker 226 and the probe 216. For example, in response to determiningthat the contamination level meets a predetermined level, thecontrollers 256 a, 256 b, and/or 206 may stop operation of the pumps 258a and 258 b. The valve 284 in the packer module 224 may be closed toisolate the packer flowline 282 from the main flowline 232.

Sampling may then be perfomed (block 602) by operating the probe 216 inthe “split-flow” configuration where the sample flow line 230 isisolated from the guard flowline 244 to allow for focused sampling. Inparticular, valves 242 and 246 may be opened and pumps 258 a and 258 bmay be operated to direct formation fluid into the downhole tool 200through the sample inlet 231 and the guard inlet 245. The valves 248 and249 may be closed so that the formation fluid flowing through the sampleflowline 230 remains isolated from the formation fluid flowing throughthe guard flowline 244 to perform focused sampling as described indetail with respect to FIG. 5, block 514.

In another embodiment, rather than first stopping operation of the pumps258 a and 258 b, sampling may be performed (block 602) by opening thevalve 242 while the pumps 258 a and 258 b continue pumping. In thisembodiment, formation fluid from both the guard inlet 245 and the packerdrains 280 may flow through the second portion 252 of the main flowline232 and commingle. The pumps 258 a and 258 b may then be reduced inspeed and the valve 284 may be closed to isolate the packer flowline 282from the main flowline 232. After closing the valve 284 in the packermodule, the valve 248 in the probe module 214 may be closed to enablethe “split flow” configuration. The valve also 249 may be closed so thatthe formation fluid flowing through the sample flowline 230 remainsisolated from the formation fluid flowing through the guard flowline 244to perform focused sampling as described in detail with respect to FIG.5, block 514.

The method 600 describe above also allows a majority of the cleanupphase to be performed using the packer 226 while performing pressuretesting (block 502). Accordingly, the pumping time for performingsampling (block 514) may be reduced because contamination levels mayreach a desired level more quickly because a large portion of thecontaminated formation fluid may be removed by the packer 226 during thepressure transient testing. Further, in the method 600, formation fluidmay be sampled from the formation 220 without moving the downhole tool200 after the pressure testing and prior to performing sampling. Becausethe probe module 214 and the packer module 224 are disposed in closeproximity to each other on the downhole tool 200, the packer 226 and theprobe 216 may be employed to withdraw formation fluid from substantiallythe same portion of the formation without moving the downhole tool 200.

The foregoing outlines features of several embodiments so that thoseskilled in the art may better understand the aspects of the presentdisclosure. Those skilled in the art should appreciate that they mayreadily use the present disclosure as a basis for designing or modifyingother processes and structures for carrying out the same purposes and/orachieving the same advantages of the embodiments introduced herein.Those skilled in the art should also realize that such equivalentconstructions do not depart from the spirit and scope of the presentdisclosure, and that they may make various changes, substitutions andalterations herein without departing from the spirit and scope of thepresent disclosure.

What is claimed is:
 1. A formation sampling method comprising: disposinga downhole tool comprising an expandable packer and an extendable probewithin a wellbore; performing pressure transient testing by setting theexpandable packer and the extendable probe to engage a wall of thewellbore and measuring a pressure response at the expandable packer andthe extendable probe while withdrawing formation fluid into the downholetool through the expandable packer; monitoring a contamination level ofthe formation fluid during the pressure transient testing; andperforming formation sampling with the extendable probe in response todetermining that the monitored contamination level meets a predeterminedthreshold.
 2. The formation sampling method of claim 1, whereinperforming pressure transient testing comprises pumping the formationfluid into the downhole tool through the expandable packer and isolatingthe extendable probe from a main flowline of the downhole tool.
 3. Theformation sampling method of claim 2, wherein monitoring contaminationlevels comprises withdrawing the formation fluid into the downhole toolthrough one or more inlets of the expandable packer and directing theformation fluid to a fluid analyzer of the downhole tool.
 4. Theformation sampling method of claim 3, wherein monitoring thecontamination level comprises determining optical properties of theformation fluid within the fluid analyzer.
 5. The formation samplingmethod of claim 1, wherein performing formation sampling compriseswithdrawing the formation fluid into the extendable probe through asample inlet and a guard inlet.
 6. The formation sampling method ofclaim 5, wherein performing formation sampling comprises directing theformation fluid from the sample inlet to a sample chamber of thedownhole tool.
 7. The formation sampling method of claim 1, whereinperforming formation sampling comprises withdrawing formation fluid intothe extendable probe while the extendable probe remains in the sameposition it was in during the pressure transient testing.
 8. Theformation sampling method of claim 1, comprising retracting theexpandable packer and the extendable probe in response to determiningthat the monitored contamination level meets the predeterminedthreshold.
 9. The formation sampling method of claim 8, moving thedownhole tool within the wellbore to dispose the extendable probe in thewellbore at a location corresponding to the expandable packer during thepressure transient testing and performing the formation sampling whenthe probe is at the location.
 10. A downhole tool comprising: anexpandable packer comprising a drain for withdrawing a first portion offormation fluid into the downhole tool; an extendable probe comprising asample inlet and a guard inlet for withdrawing a second portion offormation fluid into the downhole tool; a fluid analyzer to monitor acontamination level of the first portion of the formation fluid; acontroller configured to execute instructions stored within the downholetool to: perform pressure transient testing by setting the expandablepacker and the probe to engage a wall of the wellbore and measuring apressure response at the expandable packer and the probe whilewithdrawing the first portion of the formation fluid into the downholetool through the expandable packer; and perform formation sampling withthe extendable probe in response to determining that the monitoredcontamination level meets a predetermined threshold.
 11. The downholetool of claim 10, comprising a second fluid analyzer to monitor acontamination level of the second portion of the formation fluid. 12.The downhole tool of claim 10, comprising a first pump to direct thefirst portion of formation fluid through the downhole tool and a secondpump to direct the second portion of formation fluid through thedownhole tool.
 13. The downhole tool of claim 10, comprising: a packermodule housing the expandable packer; and a probe module housing theextendable probe, wherein the probe module is disposed in the downholetool adjacent to the packer module.
 14. The downhole tool of claim 10,wherein the fluid analyzer comprises an optical spectrometer.
 15. Thedownhole tool of claim 10 wherein the expandable packer comprises aplurality of drains spaced radially around a circumference of theexpandable packer.